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Majority of extremely hot days and many heavy rainstorms due to climate change

Research from the Institute for Atmospheric and Climate Science has shown that about 75% of extremely hot days and 18% of extreme rainfall is due to human-induced climate change.

Climate change is increasing being linked to inclement weather patterns such as heat waves and increased thunderstorms. A new study recently published in Nature Climate Change has suggested that three out of four of our hottest days can be attributed to human-induced climate change. Global warming is also the culprit of about 18% of heavy rainfalls.

Researchers Erich Fischer and Reto Knutti at the Institute for Atmospheric and Climate Science in Zurich, Switzerland, who completed the study, used 25 different climate models in calculating the odds of unusual events, such as a 1-in-100 day temperature high or a 1-in-10,000 day rainfall event, and how those changes correlate with rising global temperatures. Their results show that the global warming of 0.85 °C since the industrial revolution has caused a considerable rise in extreme highs and extreme rainfall.

“A 1-in-10,000 day heat event is something that’s only expected to happen every 30 years. But in a global-warming world, it’s turned into a 4-in-10,000 day event. Three of those hot days – or 75 per cent – would never have happened if global warming wasn’t around,” says Fischer.

“Even though warming isn’t the only cause of extreme weather, it is increasingly tipping the scales in its favour,” says Fischer. “Some people argue that these things have happened before,” he says. “Well, yes, they have. But they had been far less frequent.”

Fischer and Knutti and used their findings to predict what would happen at the 2 °C rise mark, the threshold between “acceptable” and “dangerous” climate change by many scientists. They found that the number of extreme heat days caused by global warming would just from 75% to 95%, and the extreme rainfall would jump from 18% to 40%.

“With every degree of warming it is the rarest and the most extreme events—and thereby the ones with typically the highest socio-economic impacts—for which the largest fraction is due to human-induced greenhouse gas emissions,” wrote Erich Fischer and Reto Knutti.